This invention relates to apparatus for generating a swinging motion capable of adjusting the swinging angle, and, if desired, capable of reversing the phase and stopping the swinging motion temporally.
Although many types of mechanisms have been proposed for converting a rotary motion into a swinging motion typical mechanisms include a mechanism utilizing a four member link and a mechanism utilizing a cam. The former is utilized for performing simple but accurate operations and the latter for performing complicated motions. In the cam drive mechanism, usually the motion of the follower member in one direction is effected by the surface of the cam while the motion of the follower member in the opposite direction is effected by urging the follower member against the cam surface by utilizing the weight of the follower member or a spring. However, in a high speed operation it is difficult to cause the follower member to precisely follow the cam surface so that where correct motions are required double contacts are used to restrain the movement of the follower member in two directions. This mechanism too includes a member of types. According to one type a roller is fitted in a cam groove while according to the other type a cam is located between two parallel planes. According to a typical construction of the latter type an eccentric disc is fitted between two parallel planes of a bifurcated rod so as to produce a reciprocating motion by the rotation of the eccentric disc. Where it is desired to temporally stop the reciprocating motion a triangular cam is used instead of the eccentric disc. Where an eccentric disc or a triangular cam is fitted between two flat surfaces of a bifurcated rod inaccurate fit or coarse finishing of the surfaces results in an inaccurate motion and noise so that it is necessary to accurately finish these members. Further, in the four member link mechanism it is impossible to change the length of the link during operation so that it is difficult to adjust the swingle angle of the follower link. Also in the mechanism of creating a swinging motion by utilizing a combination of a bifurcated rod and a cam it is impossible to adjust the eccentricity of the cam during operation. Accordingly, it is necessary to use an independent mechanism in order to adjust the swinging angle and the phase during operation thus requiring a complicated mechanism which is not only expensive but also accompanies fault and noise. Moreover, the curve along which the swinging motion occurs is limited by the length of the links in the four member link mechanism or by the eccentricity of the cam in the mechanism utilizing a bifurcated rod and a cam so that it is impossible to obtain a desired swinging curve. Further, the links or bifurcated rod utilized to transmit the motion are required to have a large mechanical strength to withstand tension, compression or bending force acting thereon. Accordingly, they are heavy and cause vibration.